The present invention relates to a toothpaste composition which is superior in time-dependent stability, and more particularly, it relates to a toothpaste composition which remains transparent for a long storage time
2. Description of the Prior Art
Heretofore, a variety of silica and silicate abrasives have been proposed as the abrasive for transparent toothpaste. The conventional silica or silicate abrasive, however, has some disadvantages. That is, it is poor in time-dependent stability. Where it is used for transparent toothpaste by mixing it with a transparent vehicle having substantially the same refractive index as it, it changes in refractive index in the toothpaste after a long period of storage. As a result, the toothpaste becomes poor in transparency because there occurs a discrepancy between the refractive index of silica or silicate abrasive and that of the transparent vehicle.
The conventional silica and silicate abrasives are of high refraction type having a refractive index of about 1.46. Where toothpaste is prepared with such a silica or silicate abrasive, it is necessary to prepare a transparent vehicle having approximately the same high refractive index. This is accomplished only by reducing the amount of water in the transparent vehicle and by increasing the amount of glycerin and sorbitol which have a high refractive index. However, increasing the amount of glycerin and sorbitol raises the production cost of transparent toothpaste. In addition, a large amount of glycerin and sorbitol excessively sweetens the toothpaste that contains them, and the toothpaste containing a large amount of glycerin gives a hot feeling to the mouth due to the heat of solution of glycerin. Furthermore, the toothpaste incorporated with a large amount of glycerin and sorbitol tends to rope when extruded from a tube.